Smith departs from his usual sunny-silly style for this grim, unsettling thriller, which explores the terror of intolerance and the dangers of political power. Intriguingly, the film also continues his exploration of religion (see Dogma).

Three high school students (Angarano, Gallner and Braun) use a phone app to find a 38-year-old woman (Leo) who wants to have group sex. But she's just bait. Before they know what happened, they're caged in an isolated church, where the activist pastor (Parks) explains why he's decided to take violent action against immoral society, which he blames on homosexuality. But the situation devolves into a Waco-style armed stand-off between the militant church and an ATF agent (Goodman) and his team.

The film opens with glimpses of homophobia from casual comments between teens to nasty protests outside the funeral of a hate-crime victim. As the plot continues, this combination of thoughtless bigotry and more aggressive brutality accelerates, making the film increasingly provocative. The central point is that religious and political fanatics actually cease to be what they claim to be: they're actually vigilante thugs inventing reasons for their violent actions. And the road to a massacre starts with narrow-minded self-righteousness.

Grainy, urgent camerawork makes the movie feel gritty and realistic. As the action gets increasingly grisly, Smith and Parks both struggle to depict the pastor's indignation, turning him into little more than a psychopath leading a cult of stupid, brainwashed followers. And the hardline agents trying to stop him aren't much better, although there are level-headed people on all sides. Clearly, Smith is making pointed comments on America's easily led masses, deep-seated prejudice and the US government's terrible track record in dealing with this kind of situation.

As the stand-off escalates, the film gets a bit chaotic, switching between the villains, the Federal agents and the victims trying to escape. And the depiction of Middle America gets progressively crazed as a full-on gun battle develops into a sinister political nightmare of apocalyptic proportions before a more thoughtful extended epilogue. Still, the filmmaking is skilful and sharp, with excellent acting across the board. And while there isn't much optimism in Smith's world, we should be thankful that he's exploring themes everyone else is afraid to talk about.